The present invention relates to a continuous wire stripping machine and method for stripping and separating the insulation from insulated wires, particularly solid conductor wire as opposed to stranded conductors, for the recycling thereof in the manufacturing process. The device of the present invention includes two interdigitated sets of rotary cutters in a cutter section, with each cutter having two cutting edges, only one of which is utilized at any one time, with a subsequent fixed mechanical stripping section.
2. General Background and Prior Art
To provide insulated electrical conductor wire, it is the standard common practice to extrude onto a conductive wire a plastic coating of a particular thickness covering the exterior of the wire. A typical insulating plastic used is polyvinylchloride (PVC). However, in the manufacturing process for the insulated wire, the finished product is sometimes rejected because the insulation is too thin or too thick or the inner wire is undersized or other problems exist to cause the product not to pass inspection.
In the past, if the wire was either oversized, undersized, too hard, or the elongation on the compound was not enough, often approximately 30,000 feet of finished wire was run before an inspector had time to check the wire and determine its faults. Then everything was sent to the reclamation department and, heretofore, the entire insulatng jacket and conductor were scrapped.
In the past, the PVC jacket would be stripped off by crushing it off of the inner conductor wire, often destroying the inner wire or at least substantially marring it. The inner, damaged conductor wire, generally of solid aluminum or copper, would then usually be melted. It is noted that most strippers operating on a "crushing" principle destroy an aluminum conductor insofar as direct product recycling is concerned, although a "crusher" works fairly well with copper but still produces a small amount of "wire flattening." Hence, using these prior techniques, there was a substantial loss in that both the insulating jacket and the conductor metal usually had to be totally reprocessed for the reuse thereof. Also, when using the "crushing" system of the prior art, speeds of only 100-150 feet per minute were achievable.
The prior art "crusher" stripper usually included a crude razor blade device and crushing rollers.
Other types of wire strippers besides "crushing" strippers are of course also known. For example U.S. Pat. No. 2,956,717 to Scharf (issued Oct. 18, 1960) discloses an intermittent stripper which pre-treats separated, selected portions of the insulating coating with a jet of gaseous refrigerant to embrittle it, and then the embrittled section is cut and the cut fractured on opposite sides by blunt stripping tools. U.S. Pat. No. 3,666,596 to Morton (issued May 30, 1972) discloses the technique of prestretching the coated wire in the longitudianl direction to internally break loose the outer coating from the inner wire for greater ease in stripping.
Insofar as the general wire handling aspects of the present invention, the U.S. patents to Jagger (U.S. Pat. No. 1,448,543; issued Mar. 13, 1923) and Jagger et al (U.S. Pat. No. 1,543,924; issued June 30, 1925) directed to rope untwisting apparati were brought to applicants' attention.